The word Persevere comes from the latin words 'per' meaning very and 'severus' meaning strict or harsh. As such, Severe, in our lexicon is an adjective that means very great or grave. Eg. This storm is capable of Severe damage or The judge will impose a Severe penalty for this crime.
So, if Severe means very grave, then Persevere literally means very, very grave.
In English, it means to persist, despite significant obstacles or trials such as resistance, difficulties or discouragement.
Matthew 24:13 (Douai) But he that shall persevere to the end, he shall be saved
13 On the same day Jesus went out of the house and sat by the sea. 2 And great multitudes were gathered together to Him, so that He got into a boat and sat; and the whole multitude stood on the shore.
3 Then He spoke many things to them in parables, saying: “Behold, a sower went out to sow. 4 And as he sowed, some seed fell by the wayside; and the birds came and devoured them. 5 Some fell on stony places, where they did not have much earth; and they immediately sprang up because they had no depth of earth. 6 But when the sun was up they were scorched, and because they had no root they withered away. 7 And some fell among thorns, and the thorns sprang up and choked them. 8 But others fell on good ground and yielded a crop: some a hundredfold, some sixty, some thirty. 9 He who has ears to hear, let him hear!”
Perseverence is not easy, but salvation is impossible without it. Perseverence is impossible without Grace.